1. Field of the Invention
This invention relates to a curable composition, for example a composition useful for forming a composite material comprising biopolymer particles, and to composite materials, for example mineral fiber insulation and roofing shingles.
2. Description of the Related Art
The following discussion is not an admission that anything described below is common knowledge of persons skilled in the art, or citable as prior art.
Mineral fibers used in insulation products and non-woven mats are usually bonded together with a crosslinked binder resin. The binder has to provide the resilience for recovery after packaging (in the case of insulation products) as well as stiffness and compatibility between individual fibers.
The process for making mineral fiber products such as fiberglass insulation typically includes melting minerals, sand or recycled glass, producing a molten glass stream that is passed through high pressure air fiberizers or “spinning wheels” where the glass is then spun into thin fibers and transported onto a belt to form the fiberglass insulation product. Given the enormous volume and surface area expansion, the temperature drops almost instantaneously from the red hot mineral stream to the relatively cool mineral fibers. This rapid drop in temperature facilitates the application of an aqueous polymeric binder composition immediately following the fiberizer without substantially degrading the polymer and other binder components, and more importantly, without triggering premature curing and crosslinking such that the subsequent sections of the manufacturing process can be used to control the dimensions of the fiberglass mat product. The fibers are then blown to a conveyor through a forming chamber where they are dried and cured. As part of this process, the coated mat is generally transferred to a forming or air-fluffing chamber and subsequently a curing oven to cure the binder and bond the glass fibers together. Prior to the curing process, the degree of fluffing facilitates the control over the dimensions of the particular grade of mineral fiber product.
The dominant binders for insulation and non-woven mats as well as for wood products are formaldehyde based resins, such as phenol-formaldehyde (PF), melamine-formaldehyde (MF), and urea-formaldehyde (UF) resins and the like, as well as mixed phenol/urea-formaldehyde (P/UF) resins and the like. A serious disadvantage of formaldehyde-based resins is the release of free formaldehyde to the environment during manufacturing and use, contaminating the air that we breathe which is undesirable for health and ecological reasons. Note that formaldehyde has been reported to be a human carcinogen (IARC 2004. IARC Classified Formaldehyde as Carcinogenic to Humans. IARC Press Release No. 153. International Agency for Research on Cancer, available at www.iarc.fr/en/media-centre/pr/2004/pr153.html. Substances Profile: Formaldehyde Gas. Report on Carcinogens, 11th Edition. National Toxicology Program, available at http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s089form.pdf; and National Emissions Standard for Formaldehyde in Composite Wood Products Becomes Law, found at http://www.aqs.com/DesktopDefault.aspx?mid=168&tabid=82&ItemId=30). In addition to the health and environmental problems, further compounding the problem is that the lowest cost formaldehyde based binders are based on UF resins. Therefore, UF has traditionally been the dominant binder system used in mineral fiber products, fiberglass insulation, nonwovens as well as wood products, such as particle board, plywood and oriented strand board (OSB) products. Of all the formaldehyde based resins, UF is the least stable to hydrolysis especially at elevated temperature (30-45° C., or higher) and humidity, it has commonly been the preferred binder for indoor uses (such as particle board used in kitchen cabinets, countertops, furniture, etc.), where air contamination and human exposure risks are highest. This problem recently gained visibility in the US when hurricanes Katrina and Rita devastated the Louisiana, Mississippi and Alabama coastlines. The problem was brought to the forefront following serious health and air quality complaints by displaced hurricane victims and concerns arose over high levels of formaldehyde found in some travel trailers and temporary housing (FEMA trailers). Survivors housed in the trailers were exposed to high levels of formaldehyde due to the hot and humid conditions of the local climate (Four Years Later: Formaldehyde Exposure & Emissions Standards, Product Evaluations Technology Brief by Air Quality Sciences, Inc., Volume 9, Issue 9). The somewhat more costly pure PF and MF resins are generally more stable to hydrolysis. These resins are typically used in outdoor applications, and therefore their main challenge is worker exposure during manufacturing, while in-use release of formaldehyde is less of a concern, especially in outdoor applications. Note, however, that PF resin products shipped by the resin supplier may contain a significant level of free formaldehyde, which then needs to be reduced by the downstream (e.g. fiberglass) manufacturer in a pre-reaction. This is commonly done using urea to capture most of the free formaldehyde to result in mixed P/UF binder systems. Thus, the so-called PF binders used in these applications actually are P/UF systems which are prone to more free formaldehyde release in use given the UF portion is less stable to hydrolysis, especially at temperatures between 30-45° C., or higher.
In addition, formaldehyde based binders are petroleum-based synthetic products. In an era of depleting oil reserves and increasing costs of petrochemicals, the need to wean our industries away from their dependence on foreign oil has become paramount. Plant, animal and agro-based materials are in balance with nature and are “carbon neutral”, whereas petro-based materials are not because they are “carbon positive” (see Phil Greenall and Steven Bloembergen, “New generation of biobased latex coating binders for a sustainable future”, Paper Technology 52, No. 1, Paper Industry Technical Ass'n, p. 10-14, February 2011; and Do lk Lee, Steven Bloembergen, and John van Leeuwen, “Development of New Biobased Emulsion Binders”, TAPPI, PaperCon2010 Meeting, “Talent, Technology and Transformation”, Atlanta, Ga., May 2-5, 2010). Biobased materials offer a much reduced carbon footprint, and green agro-based products are becoming more and more important in an age where greenhouse gas (GHG) emissions are escalating.
However, traditional biobased industrial materials derived from agricultural crops are generally viewed by manufacturing and packaging industries as less consistent and inferior to the dominant petrochemical-based synthetic products.
Various attempts have been made to reduce undesirable formaldehyde emissions as well as developing formaldehyde-free binders and use other synthetic oil-derived polymer resins, as well as traditional modified soluble starches, dextrins or other low performance biobased materials. However, these have serious shortcomings such as high cost, high corrosivity, high viscosity, dark color, lack of rigidity, water sensitivity, poor bond strength, etc.
A number of formaldehyde-free compositions have been developed for use as a binder for making nonwoven products.
U.S. Pat. No. 5,977,232 discloses a formaldehyde-free binder for glass wool insulation based on carboxylic acid which is corrosive due to the low pH of the system. This technology has been found to result in major corrosion problems with the equipment used to manufacture fiberglass insulation products, as well as in-use applications where metal wall studs and other metal components are being used in combination with the fiber glass insulation product.
U.S. Patent Application Publication No. 2003/0008586 discloses the use of polyvinyl alcohol (PVOH) as a formaldehyde-free binder solution for low binder nonwoven fiber mat useful for making wood product laminates. The binder produces high bonding strength with wood and is characterized by a relatively good storage stability (relative to formaldehyde resins). The binder is used at 5% concentration. The problem is the much higher cost of PVOH relative to conventional formaldehyde binder systems. In addition, since it is petroleum based it is a carbon positive material which is not environmentally preferred. Without any additional enhancer, this binder does not provide sufficient wet strength and water resistance.
U.S. Pat. Nos. 6,221,973 and 6,331,350 describe a formaldehyde-free fiberglass binder including a polyacid, such as polyacrylic acid, and a polyol, with a molecular weight less than about 1000, such as, for example, glycerol, triethanolamine, sorbitol, or ethylene glycol. A phosphorous catalyst is used to accelerate the cure of the composition. The major disadvantage of this binder is high cost and low pH which causes corrosion of fiber glass mat production equipment and during in-use applications.
PCT Patent Application Publication No. WO 2006/120523 describes a polyvinyl alcohol-based formaldehyde-free curable aqueous composition comprising PVOH crosslinked with multifunctional crosslinking agent (e.g. nonpolymeric polyacid, polyaldehyde or anhydride). Disadvantages of this system are low pH and high viscosity at relatively low solids content. The problems as mentioned above include the much higher cost of PVOH relative to conventional formaldehyde binder systems, and since it is petroleum based it is a carbon positive material which is not environmentally preferred. This binder is also corrosive due to relatively low pH (about 4) and does not provide the required water resistance.
U.S. Pat. No. 6,884,849 describes a polyalcohol-based binder composition comprising a low molecular weight polycarboxylic acid and a low molecular weight polyalcohol, such as PVOH having an average molecular weight between 200 and 13,000. The binder solution preferably comprises at least one cure catalyst or accelerator, such as sodium hypophosphite. The binder exhibits a high cure rate and provides a good recovery of the final nonwoven product. However, a practical use of such a composition for insulation production is limited because the high acidity of these binder compositions will cause corrosion of production lines and during the in-use applications. Moreover, whilst the strength of this binder is acceptable for some applications it is not as good as the commonly used formaldehyde based binders. In addition, since it is petroleum based it is a carbon positive material which is not environmentally preferred.
U.S. Patent Application Publication No. 2004/0038017 describes a binder composition containing a substantially water-dilutable or dispersible adduct of a monomeric polycarboxylic acid component and a monomeric polyol component to yield a polyester. This binder requires a much longer time (up to 15 minutes) for curing under standard curing conditions, or a much higher temperature (of about 300° C.), which a serious disadvantage.
U.S. Patent Application Publication No. 2010/0080976 discloses formaldehyde-free mineral fiber insulation product based on a combination of polycarboxylic acid, sugar and ammonia. Such a system has relatively low water resistance, is dark in color and generates ammonia emissions upon cure. In addition, since it is petroleum based it is a carbon positive material which is not environmentally preferred.
Formaldehyde free binders disclosed in U.S. Patent Application Publication No. 2007/0142596 and GB 2451719A relate to binders comprising Maillard reactants, in particular dextrose systems derived from a mixture of dextrose monohydrate, anhydrous citric acid, water and aqueous ammonia. These binders turn dark brown on curing and have poor water and biological resistance.
While these references and other prior art systems disclose various formaldehyde-free systems for insulation and non-woven mats, they all have limitations with respect to developing binders that are effective as well as environmentally friendly.
High strength fiber mats are extremely popular in the building materials industry. Most non-woven fiber mats have numerous applications, including use in roofing, siding and floor underlayment, insulation facers, floor and ceiling tiling, and vehicle parts. The most common use of fiber mats is in roofing shingles, and in particular in asphalt roofing shingles.
Various fiber mats and methods of making the same have been previously described. For example, U.S. Pat. Nos. 4,135,029, 4,258,098, 5,914,365, and 6,642,299 describe glass fiber mats made by a wet-laid process. Glass fiber mats made by the wet-laid process are formed from glass fibers held together by a binder material. The last two patents (U.S. Pat. Nos. 5,914,365 and 6,642,299) relate to improved wet web strength with styrene-maleic anhydride copolymer (SMA), styrene-acrylate copolymers, and mixtures thereof. These binders have limited application due to high cost. In addition, they are petroleum based carbon positive materials which are not environmentally preferred.
Typically, in wet processed glass fiber mats, the binder is applied in liquid form and dispersed onto the glass fibers by a curtain type applicator. Conventional wet processes strive to produce a uniform coating of binder on the glass fibers. After the binder and glass fibers have been dried and cured, the glass fiber mat is cut as desired.
A major problem in the manufacturing process and use of some known fiber mats is inadequate wet web strength. The wet web strength of wet glass mat has significant impact on runability of glass mat production and mat properties. In order to prevent the wet (glass mat) web from breaking during production, the production line speed has to be reduced due to lower wet web strength of the glass mat prior to curing. Also, lower wet web strength requires higher vacuum draw to support the wet web and minimize web breaks. But higher vacuum draw will lead to undesired mat properties, such as a high mat tensile ratio (i.e. the ratio of dry to wet tensile strengths).
Inadequate dry mat tensile strengths also can reduce the ability of the finished roofing product to resist stresses during its service lifetime on the roof. Because building materials generally, and roofing shingles in particular, are often subjected to a variety of weather conditions, the fiber mats should also maintain their strength characteristics under a wide range of conditions.
Among the attempts of improving glass fiber mat tensile strength, U.S. Pat. No. 4,430,158 claims improved tensile strength to a sized glass fiber mat by adding an anionic surfactant, such as sodium dodecylbenzene sulfonate, to the urea formaldehyde binder system, and U.S. Pat. No. 4,542,068 discloses a method of making a glass fiber mat in which a synthetic styrene butadiene binder system plus an alkoxylated alkylamine is employed, while U.S. Pat. No. 7,272,915 describes a urea formaldehyde binder modified with acrylonitrile-butadiene-styrene copolymer providing increased tensile strength. A major problem in the manufacturing process and use of fiber mats is inadequate wet web strength, which cannot be provided by a urea formaldehyde resin without an additive, as illustrated by the related art described in this paragraph. In addition, since these binders are all petroleum based they are carbon positive materials and therefore not environmentally preferred.
U.S. Pat. No. 7,268,091 discloses a urea-formaldehyde fiber binder; and a vinylpyrrolidone/acrylic acid/lauryl methacrylate terpolymer. An aqueous binder composition containing a urea-formaldehyde resin modified with a water-soluble styrene-maleic anhydride copolymer is used in the preparation of fiber mats is described in U.S. Pat. No. 6,084,021. The main disadvantage of these binders is a necessity of preparing the binder before applying it on the glass fiber mat due to a limited stability of a resin/latex mixture. In addition, since these binders are petroleum based they are carbon positive materials which are not environmentally preferred.
In summary, various attempts have been made to reduce undesirable formaldehyde emissions as well as developing formaldehyde-free binders and use traditional modified starches and dextrins or other low performance bio-based materials. However, all of these to date have serious shortcomings such as high cost, high corrosivity, high viscosity, dark color, lack of rigidity, water sensitivity, poor bond strength, etc.
Multiple disclosures have been made regarding the composition and use of various forms of biopolymer nanoparticles. For instance, U.S. Pat. No. 6,677,386 (which corresponds to WO 00/69916) describes a process for producing biopolymer nanoparticles, which in one form are starch nanoparticles. In the process, the biopolymer is plasticized using shear forces, and a crosslinking agent is added during the processing. After the processing, the biopolymer nanoparticles can be dispersed in an aqueous medium. One version of the process results in starch nanoparticles which are characterized by an average particle size of less than 400 nanometers. The nanoparticles can be used as a matrix material wherein the matrix material may be a film-forming material, a thickener, a rheology modifier, an adhesive or an adhesive additive (tackifier). The nanoparticles or dispersions thereof may also be used for their barrier properties, as a carrier, fat replacer or medicament for mitigating dermal disorders. Further examples of applications for the nanoparticles or dispersions thereof are in the paper-making and packaging industry, agriculture and horticulture fields. The nanoparticles can also be used as excipients or carriers in medicines, where they may be complexed or covalently coupled to active substances such as slow-release drugs. The nanoparticles can also be processed into a foam at relatively high density.
Other uses of the nanoparticles of U.S. Pat. No. 6,667,386 can be found in: (i) U.S. Pat. No. 7,160,420 which describes the use of the starch nanoparticles as a wet-end additive in papermaking pulp slurry, or applied to the surface of the paper as a surface sizing agent; (ii) U.S. Pat. No. 6,825,252 which describes the use of the starch nanoparticles in a binder in a pigmented paper coating composition; (iii) U.S. Pat. No. 6,921,430 which describes the use of the starch nanoparticles in environmentally friendly adhesives; and (iv) U.S. Patent Application Publication No. 2004/0241382 which describes the use of the starch nanoparticles in an adhesive for producing corrugated board. The disclosure of these patents and published applications, and of all other publications referred to herein, are incorporated by reference as if fully set forth herein.
The invention in U.S. Pat. No. 6,667,386 relates to a process for producing biopolymer nanoparticles which in one form are starch nanoparticles characterized by an average particle size of less than 400 nanometers. The structure of the biopolymer nanoparticles has been described in the literature (see Bloembergen et al., “Specialty Biobased Monomers and Emulsion Polymers Derived from Starch”, 2010 PTS Advanced Coating Fundamentals Symposium, Munich, Germany, Oct. 11-13, 2010). In dry form, the product consists of larger agglomerates with an average agglomerate particle size of ˜300 μm (300,000 nm.), from which nanoparticles are released when they are dispersed in water. In dispersed form, the biopolymer nanoparticles exist as insoluble colloidal particles that form a biopolymer latex dispersion with an average size of ˜100 nanometers. Each of the nanoparticles can be thought of as internally crosslinked macromolecular units with intra-particle crosslinks (FIG. 1). No inter-particle crosslinks exist, as this would result in poor rheology and reduced binding power (reduced surface area). Excellent paper coating binding strength and rheological properties (superior machine runability) have been reported by coated paper and board manufacturers and paper industry experts (see Klass, C. P., “New Nanoparticle Latex offers Natural Advantage”, Paper360° Magazine, p. 30-31, January, 2007; Figliolino et al., “Reducing Carbon Footprint with Biolatex”, Paper360° Magazine, p. 25-28, August, 2009; Lee et al., “Development of New Biobased Emulsion Binders”, TAPPI, PaperCon2010, “Talent, Technology and Transformation”, Atlanta, Ga., May 2-5, 2010; Greenall et al., “New generation of biobased latex coating binders for a sustainable future”, Paper Technology 52, No. 1, Paper Industry Technical Ass'n, p. 10-14, February 2011; and Oberndorfer et al., “Coating & print performance of biobased latex in European graphic papers”, TAPPI, PaperCon2011, “Rethink Paper: Lean and Green”, Cincinnati, Ohio, May 1-5, 2011). The biopolymer latex binder provides a high performance substitute to the petrochemical-based binders used in coated paper and paperboard manufacturing processes at a lower cost per pound. Carboxylated or acrylonitrile or otherwise modified styrene butadiene (SB latex) and styrene acrylate (SA latex) are the dominant petrochemical-based binders used in coated paper and paperboard manufacturing. Currently, the industry consumes over 4 billion pounds of SB and SA latex per annum. As the price of oil continues to escalate, and as the price of synthetic binders has increased by more than 100% over the past few years, paper producers have faced increased production costs forcing them to find efficiencies, pass increases on to the consumer, or cease production. The biopolymer latex binder of U.S. Pat. No. 6,677,386 provides performance that is comparable to the petro-based SB and SA latex products for important paper properties such as coating gloss, brightness, whiteness, fluorescence, ink gloss, and printability, while providing superior performance to SB and SA Latex for water retention, opacity, dry pick, print mottle, porosity (blister resistance) and paper stiffness.